A Reevaluation of the Search Cycle of Planktivorous Arctic Graylings Thymallus arcticus

1988 ◽  
Vol 45 (1) ◽  
pp. 187-192 ◽  
Author(s):  
Barbara I. Evans ◽  
W. John O'Brien
Keyword(s):  
Feeding Behavior ◽  
Pause Duration ◽  
Search Efficiency ◽  
Turn Angle ◽  
Body Form ◽  
Arctic Grayling ◽  
Saltatory Search ◽  
Thymallus Arcticus ◽  
The Relationship ◽  
Strategy Searching

Planktivorous arctic grayling, Thymallus arcticus, were previously believed to forage using a cruise strategy, searching for prey while swimming, while other planktivores have been found to search while stationary, a strategy termed "saltatory search." Comparing the predicted components of cruise and saltatory search, we observed that the planktivorous feeding behavior of the grayling was more consistent with the strategy of saltatory search. Although the grayling appear to swim continuously, they actually pause before making turns. Swim speed is reduced with decreased prey detectability, as would be expected of a cruise searcher; however, this behavior is believed to be a result of fin placement and body form constraints. Pause duration, run length, and run turn angle were observed to vary when grayling fed on prey of different sizes, all in a manner consistent only with saltatory search. The relationship between the ability to locate prey and the components of search suggests that the grayling alter the way they search for different prey, possibly as a means of increasing search efficiency.

Behavior as a window on physiology: a simple apparatus for recording caterpillar feeding.

1992 ◽  
Vol 262 (6) ◽  
pp. S9 ◽  
Author(s):  
E Bowdan
Keyword(s):  
Feeding Behavior ◽  
Control Mechanisms ◽  
Inexpensive Method ◽  
Simple Apparatus ◽  
Physiological Processes ◽  
Wide Range ◽  
Relationship Of ◽  
The Relationship

Regulation of feeding is a fundamental element of homeostasis. This is reflected in the similarity of control mechanisms in a wide range of animals, including insects and humans. A close examination of feeding behavior can illuminate the physiological processes driving regulation. A simple, inexpensive method for recording fine details of feeding by caterpillars is described. Possible experiments, interpretation of the data, and the relationship of observations to the underlying physiology, are outlined.

Calculation of Incremental Force of External Steel in Simply Supported Externally Prestressed Beams

2010 ◽  
Vol 163-167 ◽  
pp. 1719-1723
Author(s):  
Di Hu ◽  
Zhi Wu Yu
Keyword(s):  
Concrete Beam ◽  
Turn Angle ◽  
Simply Supported ◽  
Novel Approach ◽  
Beam Equations ◽  
Time Dependent Effect ◽  
Relationship Of ◽  
Train Of Thought ◽  
The Relationship ◽  
Prestressed Beams

Considering the relationship of displacement and turn angle in anchorages and deviators between the externally prestressed steel and concrete beam under the action of load in simply supported externally prestrressed beam, equations on solving the incremental force in externally prestressed steel are established. The presented novel approach and the train of thought can be easily extended to analyze time-dependent effect for externally prestressed beams. The example shows that the theoretical values based on the presented formulae are agreeable with the results obtained by other methods.

Positive association between experimental cortisol increases and cage-measures of feeding behavior in wild-caught gerbils

2021 ◽  
pp. 1-9
Author(s):  
Franklin Sargunaraj ◽  
Justin R. St. Juliana ◽  
Cynthia J. Downs ◽  
Irina S. Khokhlova ◽  
Lee Koren ◽  
...  
Keyword(s):  
Blood Serum ◽  
Feeding Behavior ◽  
Hormone Level ◽  
Positive Association ◽  
Serum Levels ◽  
Enzyme Linked Immunosorbent Assay ◽  
Time Period ◽  
Cortisol Levels ◽  
And Behavior ◽  
The Relationship

Abstract Glucocorticoid hormone levels vary within a forager based upon environmental stressors such as illumination and riskier habitats, and a forager’s response to environmental variables depends upon its glucocorticoid levels. Here, we report on a laboratory experiment in which we manipulated cortisol in Allenbyi’s gerbils (Gerbillus andersoni allenbyi) to test the relationship between cortisol and behavior. We then quantified the resulting blood cortisol levels and feeding behavior in gerbils. Thirty gerbils were injected with 21-day slow-release cortisol pellets drawn from 5 different dosages. We quantified the physiological response to pellet implantation in gerbils by measuring cortisol level in blood serum using ELISA (Enzyme Linked Immunosorbent Assay). We fed gerbils daily by mixing millet seeds into the sand inside rodent cages and measured the remaining seeds the following day to quantify feeding efforts. Some evidence supports that subcutaneous supplementation of glucocorticoids (GCs) in the gerbils led to higher blood serum levels. Cortisol levels varied according to time period of measurement. Gerbils that received lower dosages consumed most of the food presented to them when compared to those receiving the highest doses. In this manner, we delineate a pattern on cortisol hormone level variation over time following dosing and consequences in feeding behavior.

Energetic status and bioelectrical impedance modeling of Arctic grayling Thymallus arcticus in interior Alaska Rivers

2019 ◽  
Vol 102 (11) ◽  
pp. 1337-1349
Author(s):  
Jeffrey A. Falke ◽  
Lauren T. Bailey ◽  
Kevin M. Fraley ◽  
Michael J. Lunde ◽  
Andrew D. Gryska
Keyword(s):  
Bioelectrical Impedance ◽  
Arctic Grayling ◽  
Interior Alaska ◽  
Impedance Modeling ◽  
Thymallus Arcticus

Selection of Positions by Drift-Feeding Salmonids in Dominance Hierarchies: Model and Test for Arctic Grayling (Thymallus arcticus) in Subarctic Mountain Streams, Interior Alaska

1992 ◽  
Vol 49 (10) ◽  
pp. 1999-2008 ◽  
Author(s):  
Nicholas F. Hughes
Keyword(s):  
Bottom Topography ◽  
Lateral Diffusion ◽  
Distribution Patterns ◽  
Mountain Stream ◽  
Physical Habitat ◽  
Dominance Hierarchies ◽  
Arctic Grayling ◽  
Drift Feeding ◽  
Stream Salmonids ◽  
Thymallus Arcticus

In this work I describe a model to predict position choice by each individual in a dominance hierarchy of drift-feeding stream salmonids. This is an adaptation of Hughes and Dill's model (1990. Can. J. Fish. Aquat. Sci. 47: 2039–2048) of position choice by solitary fish. I have included the effect that prey consumption, lateral diffusion of drifting invertebrates, and entry of invertebrates into the drift have on the density of prey downstream of feeding fish and the restrictions that dominant fish place on freedom of choice by their subordinates. l assume that each fish chooses the most profitable position that its rank in the hierarchy will allow. There was an encouraging match between the distribution patterns predicted by the model and the distribution patterns actually adopted by Arctic grayling (Thymallus arcticus) in two pools of a mountain stream. This result suggests that Arctic grayling locate and rank positions based on their profitability. The predictions of reduced models, and the location of positions in relation to bottom topography and current flow, suggest that the physical habitat forms the template for distribution patterns by determining the location and ranking of the most profitable positions.

scholarly journals Consumption of Shrews, Sorex spp., by Arctic Grayling, Thymallus arcticus

2004 ◽  
Vol 118 (1) ◽  
pp. 111 ◽  
Author(s):  
Jonathan W. Moore ◽  
G. J. Kenagy
Keyword(s):  
Stable Isotopes ◽  
Dietary Habits ◽  
Riparian Zones ◽  
Stream Fishes ◽  
Nitrogen Stable Isotopes ◽  
Arctic Grayling ◽  
Thymallus Arcticus ◽  
Southwestern Alaska

In an investigation of the dietary habits of Arctic Grayling (Thymallus arcticus) we found that two individuals out of 93 sampled in southwestern Alaska (approximately 59°N, 159°W) contained a total of five shrews (Sorex spp.). These shrews contained enriched levels of nitrogen stable isotopes, suggesting utilization of nutrients derived from salmon. We hypothesize that normally terrestrial shrews accidentally enter streams while foraging along the productive riparian zones of creeks with high densities of salmon. Shrews are apparently susceptible to opportunistic predation by resident stream fishes, including Arctic Grayling, when they enter the streams.

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